The link you want:

https://grandideastudio.com/portfolio/security/ledger-hardwa...

They should have posted the weight with and without the device in it.

Also: never leave empty space in a hardware key, pot the whole thing in epoxy.

I heard they reduced the battery size to make space for their chip.

This one too (pardon the AI slop): https://www.tibane.net/research/ledger-nano-x-implant

Is that safe for devices containing a lithium battery?

They could x-ray it, carve out epoxy with nothing inside, put the logger, apply epoxy.

Take off the case, put your own entire module in, put the case back in. Epoxy doesn't solve much.

...frankly, selling one as DIY kit have highest chance for tamper resistance. Tho pretty untenable with small SMD components sadly